It has long been recognized that loss of lubricating oil pressure for an internal combustion engine can result in serious mechanical damage to the engine components if the engine continues to run. Early on, inventors devised valves for shutting off the flow of fuel to an engine in response to the loss of lubricating oil pressure. See, for example, U.S. Pat. No. 1,339,798 granted May 11, 1920 to G. W. Thompson for "Valve."
An improved valve for this same purpose is disclosed in my U.S. Pat. No. 4,067,348 granted Jan. 10, 1978 for "Fuel Shutoff Valve." The valve disclosed in this patent displays some sensitivity to variations in the pressure of the fuel passing therethrough. In other words, changes in fuel pressure, which are experienced with changes in engine speed, can cause that valve to operate to terminate or impede fuel flow at different oil pressures. Consequently, it has been the practice to install this valve upstream of, i.e., on the suction side of, the fuel pump in order to minimize the fuel pressure variations to which the valve is subjected.
All valves, filters and the like, on the suction side of the fuel pump are subjected to below atmospheric pressure so that if any of these devices leak, they allow air to enter the fuel system. This can be deleterious, particularly to diesel engines. Therefore, it is preferred that any fuel control valve and any filter associated therewith be located on the downstream, or outlet, side of the fuel pump. But this location, of course, subjects the fuel control valve to significant fuel pressure variations with changes in engine speed. Others have devised fuel control valves for installation between the fuel pump and the engine. See, for example, U.S. Pat. No. 3,148,671 granted Sept. 15, 1964 to F. Botterff et al. for "Fuel Control for Internal Combustion Engines" and U.S. Pat. No. 3,523,521 granted Aug. 11, 1970 to J. E. Goodwin for "Pressure Responsive Engine Fuel Device with Variable Shutoff Point." The Bottorff et al. patent discloses a valve the operation of which can be influenced by the rate at which fuel flows therethrough. The Goodwin patent discloses a valve structure which is intended to take advantage of variations in fuel pressure for the very purpose of changing the lubricating oil pressure at which the valve is closed to shut off the flow of fuel.
The present invention is premised on the belief that the most useful fluid flow control valve is one having a reliable and predictable response to lubricating oil pressure. The valve which always opens and closes at predetermined lubricating oil pressures without regard to pressure in the fuel line or the rate of flow of fuel through the valve is deemed to best meet the needs of engine operators. The principal objective of this invention is the provision of such a valve.